Light Snowfall (1" - 4") on Tuesday Dec 23 For NYC Region (Discussion & Observations)

[snywx]

2 hours ago, MJO812 said:

Steve D

Def donot see 3-6” up here lol.. 1-2” up here is prob the limit 

[IrishRob17]

1 minute ago, snywx said:

Def donot see 3-6” up here lol.. 1-2” up here is prob the limit 

Agreed. Looking forward to some mood flakes for Festivus.  

[wxman]

7 minutes ago, IrishRob17 said:

Agreed. Looking forward to some mood flakes for Festivus.  

for the restofus..........

[Northof78]

1" - 3" nice little storm coming with temps in 20s for almost all, enjoy it! 

[eduggs]

Warm advection precip especially with a parent low significantly separated from the overrunning can be locally unpredictable. It can be banded with distinct maxes and mins that defy typical geographical snowfall distributions. The inter- and intra-model variability supports this. As usual, this will be an interesting nowcast. With surface temperatures near or just above freezing, snow could accumulate pretty much anywhere. Can't really count anyone out for a coating to about 3". I don't think this event will reveal its character until the last moment. Hopefully when it does early Tue it appears wintry and festive.

[North and West]

Whatever falls will melt before Christmas anyway lol

good to see you before the holiday, Uncle Scrooge


.

[psv88]

5 minutes ago, North and West said:

good to see you before the holiday, Uncle Scrooge


.

Yea no that’s not me. Just being realistic. 

[coastalplainsnowman]

53 minutes ago, IrishRob17 said:

Agreed. Looking forward to some mood flakes for Festivus.  

We definitely have the airing of grievances part covered.

[IrishRob17]

10 minutes ago, psv88 said:

Yea no that’s not me. Just being realistic. 

And yet you still felt the need to point out the melting. Interesting. 29/14 and blustery. 

[psv88]

Just now, IrishRob17 said:

And yet you still felt the need to point out the melting. Interesting. 

Yea it’s a weather discussion board. We talk about weather, good, bad, ugly. Sorry I hurt your feelings 

[donsutherland1]

No changes in thinking at this time. With marginal temperatures and light precipitation rates, most of the New York City area will probably see little more than a coating. The City will likely see temperatures remain above freezing for most or all of the storm. A trace of snow cannot be ruled out for parts of the City. Nearly three-quarters of events with temperatures above freezing saw no measurable snowfall while just one-in-six had 1" or more in Central Park's climate record. It is possible that the precipitation could mix with or end as some light rain or drizzle in and around New York City.

The distant northern and western suburbs continue to have the best chance of seeing 1"-2", as readings will likely be near or perhaps even a little below freezing during much of the event. 

The latest WPC maps for 24-hour probabilities of 1" or more and 2" or more snowfall are below:

[MJO812]

HRRR shifted south

 

[Birds~69]

2 hours ago, snywx said:

Def donot see 3-6” up here lol.. 1-2” up here is prob the limit 

Steve D, enough said....

[eduggs]

Considering just about all guidance has 0.2" liquid or more across NNJ and SENY and a snow-supporting model profile, those WPC snow maps look low.

You would seemingly have to go against model consensus to come up with those probabilities. Or maybe they are heavily skewed towards the GEFS. Either way, the lack of granularity across our region makes it only modestly useful.

[snywx]

11 minutes ago, eduggs said:

Considering just about all guidance has 0.2" liquid or more across NNJ and SENY and a snow-supporting model profile, those WPC snow maps look low.

You would seemingly have to go against model consensus to come up with those probabilities. Or maybe they are heavily skewed towards the GEFS. Either way, the lack of granularity across our region makes it only modestly useful.

Are you thinking more than 2" here in the 84 corridor? Im thinking 2" is prob the upper limits in this area. Maybe some 3-4" amounts in the Catskills 

[MJO812]

Nam shifted north 

 

[eduggs]

3 minutes ago, snywx said:

Are you thinking more than 2" here in the 84 corridor? Im thinking 2" is prob the upper limits in this area. Maybe some 3-4" amounts in the Catskills 

I'm thinking 2" as the average across I-84 - not the upper limit - but with a wide range and maybe a funky regional distribution. I wouldn't expect uniform and consistent precipitation. I would guess the precip. shield is more banded and variable with winners and losers. But it's just a guess really.

[Krs4Lfe]

1 hour ago, eduggs said:

Considering just about all guidance has 0.2" liquid or more across NNJ and SENY and a snow-supporting model profile, those WPC snow maps look low.

You would seemingly have to go against model consensus to come up with those probabilities. Or maybe they are heavily skewed towards the GEFS. Either way, the lack of granularity across our region makes it only modestly useful.

They are probably favoring in the white rain due to warmer temperatures at the onset, which will lead to minimal accumulation in the urban zones of the tri state area. Either way, that should make for a solid 1-3” further inland 

[eduggs]

Other than the usual weird jump by the NAM, so far 0z looks similar to previous cycles. Changes look like noise to me... Still looks like a coating to 3" or so from the south coasts to far northern suburbs with a ragged and unpredictable gradient...

The variable and inconsistent geographic distribution of snowfall between models suggests a low probability forecast. Model changes are being driven by very minor differences in vorticity and micro-short-waves.

The WRF-NSSL is the weenie model of 0z with 3-5" right through the NYC metro. Unlikely but probably not impossible.

[eduggs]

10 minutes ago, Krs4Lfe said:

They are probably favoring in the white rain due to warmer temperatures at the onset, which will lead to minimal accumulation in the urban zones of the tri state area. Either way, that should make for a solid 1-3” further inland 

The WPC maps have <10% probability for 2" of snow in the far northern reaches of the OKX forecast area, including elevations above 1000ft. That should have nothing to do with "white rain." Those areas might not get 2" of snow. But I would like to know what the basis is for assigning a probability of less than 1 in 10 chance.

[donsutherland1]

Not much has changed overnight. A coating of snow seems likely in New York City and its nearby suburbs due to a combination of marginal temperatures and light precipitation rates. 1"-2" is likely in the distant northern and western suburbs. There could be some 3" amounts in places like Binghamton. Overall, the system remains on course to be a minor one.

The latest WPC maps:

For reference: the latest NWS Map:

[donsutherland1]

10 hours ago, eduggs said:

The WPC maps have <10% probability for 2" of snow in the far northern reaches of the OKX forecast area, including elevations above 1000ft. That should have nothing to do with "white rain." Those areas might not get 2" of snow. But I would like to know what the basis is for assigning a probability of less than 1 in 10 chance.

The WPC mapping tool isn't topographic. Hopefully, as AI allows for greater detail at reduced computing power, future maps will be topographic in nature to better capture elevation-related accumulations.

[MJO812]

Nam has about an inch for the coast

[RU848789]

12Z NAM12km, NAM3km, FV3 and RGEM all show 1" or more along and N of 78, including for NYC.  We might get an overperformer if we're lucky.  

[SnowGoose69]

6 minutes ago, RU848789 said:

12Z NAM12km, NAM3km, FV3 and RGEM all show 1" or more along and N of 78, including for NYC.  We might get an overperformer if we're lucky.  

They're all sloppy with the QPF fields...if that ends up being more a consolidated WAA snow shield we may see this overperform. Once again though the NAM was pretty bad with this til we got inside 36.  I've been saying for awhile now, avoid that model beyond 36, sometimes it does okay 36-48 but often time its the final day or day and a half where its reliable.

[MJO812]

Gfs colder for tomorrow

[BoulderWX]

Just now, MJO812 said:

Gfs colder for tomorrow

love the 3.3 right over my backyard but highly skeptical - believe this is a Trace - 2" for most of the forum. I'll happily take it to add to the holiday festivities. 

[Krs4Lfe]

4 minutes ago, BoulderWX said:

love the 3.3 right over my backyard but highly skeptical - believe this is a Trace - 2" for most of the forum. I'll happily take it to add to the holiday festivities. 

Should be nice to look at as it falls but I would imagine it will all melt within a day or so. North and west of NYC might have enough to stick around until Christmas but NYC barely sticks even on a colder day  Hopefully NYC can squeeze out one inch and get to the magic 4” mark for December 

[SnowGoose69]

1 minute ago, Krs4Lfe said:

Should be nice to look at as it falls but I would imagine it will all melt within a day or so. North and west of NYC might have enough to stick around until Christmas but NYC barely sticks even on a colder day  Hopefully NYC can squeeze out one inch and get to the magic 4” mark for December 

The temps did go to hell on this from what the models showed 3 days ago which is not surprising since it was always going to be a SW flow event in the low levels.  I think its a case where you need it to be snowing by 8-9z.  The longer you allow the DPs to rise on the SW flow the harder it will be to get down to 32-33 and get accumulation.

[Snowlover11]

Trace to an inch in and around the city.

1-3” away from the coast and North of 80. Expect the less, Hope for the greater. 3” might be pushing it unless your the far north and west crew.